107 research outputs found
Comment on ‘‘Geodynamic evolution of the SW Europe
Ribeiro et al. [2007] have presented a geodynamic
view of the SW Iberia Variscides based on data from
Portugal. Their treatment of already published data is commendable,
and the knowledge gained will surely encourage
the discussion of the SWEurope Variscides. However, in our
opinion, Ribeiro et al.’s modeling and interpretation of the
Ediacaran–Lower Ordovician ( 560–470 Ma) geodynamic
evolution are of limited value. In this regard, they based their
analysis of the Ossa-Morena Zone (OMZ) on assumptions
which are contradicted by recent published data. Ribeiro et al.
ignored recent progress in the OMZ Ediacaran-Ordovician
stratigraphy and, as a consequence they misunderstood
the structure of domains overprinted by strong Variscan
(Carboniferous) deformation and metamorphism
O recurso especial no Superior Tribunal de Justiça e a introdução da repercussão geral
Trabalho de Conclusão de Curso (graduação)—Universidade de Brasília, Faculdade de Direito, 2017.O Superior Tribunal de Justiça, através do Recurso Especial, cumpre o papel de uniformizar a interpretação da legislação infraconstitucional no país. Com efeito, embora já haja restrições para a interposição desse recurso, ainda é grande o número de processos que chegam ao STJ – muitos sem necessidade. Em vista disso, o Legislativo tem buscado diferentes propostas para filtrá-los. Uma delas é acrescentar o requisito da repercussão geral ao Recurso Especial. O presente trabalho analisará esse requisito de admissibilidade (sua aplicabilidade e necessidade), mediante o estudo das origens e das funções do STJ, do recurso especial e da repercussão geral.The Superior Court of Justice, through the Special Appeal, aims to standardize the interpretation of infraconstitutional legislation in the country. In fact, although there are already restrictions on the filing of these appeals, the number of cases that reach the SCJ is still large - many unnecessary. In view of this, the Legislative Branch has sought different proposals to filter these appeals. One of them is to add the requirement of general repercussion to the Special Appeal. The present study will analyze this admissibility requirement (its applicability and necessity), by studying the origins and functions of the SCJ, the Special Appeal and the general repercussion
Tectonothermal analysis of high-temperature mylonitization in the
Mylonites in pelitic and quartzofeldsphatic gneisses from the Ouguela tectonic unit (Coimbra–Córdoba shear zone, SW Iberian Massif) have
been studied as an example of high-temperature ductile deformation associated with transcurrent tectonics. Detailed microstructural and P–T
analysis indicates that ductile deformation evolved from a metamorphic peak at approximately 650–750 °C and 7.5–9.5 kbar (quartzofeldsphatic
gneisses) and 730–790 °C and 7.5–9.5 kbar (pelitic gneisses) to retrograde conditions at 500–575 °C and 4.5/5.5–6.5/7.5 kbar (quartzofeldsphatic
gneisses) and 525–600 °C and 3.5/4.5–5.5/7.5 kbar (pelitic gneisses). Following the metamorphic peak, exhumation was very fast. The P–T
trajectory, which does not reach the curve for granite melting, is distinct that of isothermal decompression. Instead, the progressive and
contemporaneous decrease in pressure and temperature was a direct response to strong heat dissipation along the contacts between the ascending
slice and the adjacent blocks. The horizontal component of exhumation path, calculated for middle and shallower crustal levels, sum to ca. 57 km
to 94 km (for the pressure peak). Assuming this offset acted in the Viséan during a time interval of ca. 9 Ma, the estimated exhumation horizontal
slip rate is in the order of 6.3 to 10.4 mm/yr, which corresponds to an exhumation oblique-slip exhumation rate of 6.6 to 10.7 mm/yr (for ductile
deformation). These values indicate that the transcurrent tectonic displacements accommodated by these mylonitic are similar to those of modern
intra-continental shear zones, such as the still active Karakoram Fault (8.3 mm/yr) in the Himalayas. The Coimbra–Córdoba shear zone is
therefore a typical intra-continental transcurrent zone with ten-to-one hundred kilometre along-strike mass movement of material that aided the
exhumation of deep crustal rocks. Study of this large-scale structure in the SW Iberian Massif is therefore central to models of orogenic
deformation during the amalgamation of Pangea
Crustal growth and deformational processes in the northern
The aim of this article is to present a compilation of available information on
the Évora Massif based on structural mapping, whole-rock geochemistry, recognition
of metamorphic mineral assemblages, and geothermobarometry. In our view, transcurrent
movements responsible for strong orogen-parallel stretching were dominant
and had a major role in the geodynamic evolution of this part of Ossa-Morena zone
(southwest Iberian Massif). Cadomian and Variscan orogenic events separated by a
period of intense rifting were the cause for the composite distribution of zones with
contrasting metamorphic paths, the structural complexity, the variety of lithological
associations, and the sequence of deformation events and magmatism. The proposed
geodynamic reconstruction for this segment of the northern Gondwana continental
margin includes three main stages in chronological order: (1) Neoproterozoic accretion
and continental magmatic arc developing, dismantling, and reworking, followed by late-“orogenic” magmatism; (2) Lower Paleozoic crustal thinning, block tilting,
and mantle upwelling, induced by generalized rifting, leading to the formation of
marine basins with carbonate platform sediments and thick accumulations of volcaniclastic
and terrigenous sediments, contemporaneous with normal and enriched
mid-oceanic ridge basalt–type magmatism; and (3) Upper Paleozoic transpressional
orogenesis resulting from obliquity of convergence and the geometry of the involved
blocks. The third stage includes the tectonic inversion of Lower Paleozoic basins,
crustal thickening, the exhumation of high- to medium-pressure rocks and partial
exhumation of high-grade metamorphic lithologies (controlled by local transtension
and major detachments), the formation of synorogenic basins fi lled with volcanicsedimentary
sequences, and fi nally, the emplacement of late Variscan granodiorites
and granites
Grupos estratégicos na indústria química mundial: 2004-2008
Bibliografia: p. 374-377A indústria química fabrica produtos que são utilizados em uma ampla variedade de setores: agricultura, manufatura, construção e serviços, principalmente com base em insumos de origem fóssil, como óleo e gás natural. A busca de economias de escala na indústria ocasiona um fenômeno de supercapacidade intermitente, que tende a deprimir as margens de seus participantes no longo prazo. Ao lado disso, essa indústria tem importância estratégica para seus países de origem e vem sendo cada vez mais pressionada em questões de regulação ambiental. Este estudo avalia o desempenho de segmentos de negócios na indústria química mundial, em termos de sua lucratividade, com base em uma amostra com os resultados financeiros de 269 empresas de capital aberto originárias de 32 países, entre os anos de 2004 e 2008. Além de indicar os negócios mais atraentes nessa indústria, o trabalho ressalta que a escala é, em geral, relevante, que empresas focadas alcançam melhores resultados do que as empresas diversificadas, quando se consideram indicadores de desempenho de mercado, e que a posição geográfica e o estágio de desenvolvimento do país de origem das empresas desempenham papel importante na criação de valor para os investidores. O estudo começa com uma breve descrição da indústria química, segue com uma discussão sobre as fontes do desempenho de empresas, com especial atenção ao conceito de grupos estratégicos nele empregado. São então mencionados os procedimentos metodológicos e, em seguida, apresentados e discutidos os resultados dos testes estatísticos. Ao final, são indicadas as contribuições, ressaltando-se algumas implicações para o caso da indústria química brasileira
Zircon geochronology of intrusive rocks from Cap de Creus, eastern Pyrenees
New petrological and U–Pb zircon geochronological information has been obtained from
intrusive plutonic rocks and migmatites from the Cap de Creus massif (Eastern Pyrenees) in order
to constrain the timing of the thermal and tectonic evolution of this northeasternmost segment of
Iberia during late Palaeozoic time. Zircons from a deformed syntectonic quartz diorite from the
northern Cap de Creus Tudela migmatitic complex yield a mean age of 298.8±3.8 Ma. A syntectonic
granodiorite from the Roses pluton in the southern area of lowest metamorphic grade of the massif
has been dated at 290.8±2.9 Ma. All the analysed zircons from two samples of migmatitic rocks
yield inherited ages from the Precambrian metasedimentary protolith (with two main age clusters at
c. 730–542 Ma and c. 2.9–2.2 Ga). However, field structural relationships indicate that migmatization
occurred synchronously with the emplacement of the quartz dioritic magmas at c. 299 Ma. Thus, the
results of this study suggest that subduction-related calc-alkaline magmatic activity in the Cap de
Creus was coeval and coupled with D2 dextral transpression involving NNW–SSE crustal shortening
during Late Carboniferous – Early Permian time (c. 299–291 Ma). Since these age determinations are
within the range of those obtained for undeformed (or slightly deformed) calc-alkaline igneous rocks
from NE Iberia, it follows that the Cap de Creus massif would represent a zone of intense localization
of D2 transpression and subsequent D3 ductile wrenching that extended into the Lower Permian during
a transitional stage between the Variscan and Cimmerian cycles
Deciphering a multi-event in a non-complex set of detrital zircon U–Pb ages from Carboniferous graywackes of SW Iberia
The determination of U–Pb ages from detrital zircons of sedimentary rocks using LA-ICP-MS has been widely
used for the purpose of provenance analysis. One problem that frequently arises is finding a population that
appears to be non-complex despite several perceptible age peaks in its spectrum. These peaks are qualitatively
defined by means of relative probability diagrams, or PDFs, but it is difficult to quantify their statistical significance
relative to a zircon forming multi-event. Thus, can a multi-event in a non-complex set of detrital zircon
U–Pb ages be deciphered and characterized?
The aim of this study is to attempt to provide an answer to this question by means of statistical analysis. Its
objectives are: a) to determine the best minimum number of zircon age populations (peaks), BmPs, b) for the
characterization of each peak in terms of age and event duration; c) to compare the results obtained from two
datasets showing similar zircon ages; and d) to demonstrate the usefulness of deciphering these BmPs. First,
cluster analysis is carried out, aimed at grouping zircon ages into a set of consistent clusters. A Gaussian Kernel
function is then fitted to each cluster and summed to obtain a theoretical PDFm (modeled probability density
function). Finally, the selected modeled PDFm (that built on the BmPs) is that which reports the lowest number
of peaks for which the difference as compared with the original gPDF (global probability density function) is
equal to or below 5%. Deciphered BmP peaks can be characterized and used for characterizing and providing
an understanding of related event(s).
A geological interpretation, based on the results obtained, is attempted. This includes a robust measure for
maximum age of deposition for both Cabrela and Mértola graywackes
Zircon U–Pb geochronology of paragneisses and biotite
Sensitive high-resolution ion microprobe U–Th–Pb age determinations on detrital and
inherited zircon from the E ´ vora Massif (SW Iberian Massif, Portugal) provide direct evidence for
the provenance of the Ossa–Morena Ediacaran basins (Se´rie Negra) and a palaeogeographical link
with the West African craton. Three samples of the Se´rie Negra paragneisses contain large components
of Cryogenian and Ediacaran (c. 700–540 Ma) detrital zircon, but have a marked lack of
zircon of Mesoproterozoic (c. 1.8–0.9 Ga) age. Older inherited zircons are of Palaeoproterozoic
(c. 2.4–1.8 Ga) and Archaean (c. 3.5–2.5 Ga) age. The same age pattern is also found in the
Arraiolos biotite granite, which was formed by partial melting of the Se´rie Negra and overlying
Cambrian rocks. These results are consistent with substantial denudation of a continental region
that supplied sediments to the Ediacaran Ossa–Morena basins during the final stages of the
Cadomian–Avalonian orogeny (peri-Gondwanan margin with principal zircon-forming events
at c. 575 Ma and c. 615 Ma). Combined with the detrital zircon ages reported for rocks of the
same age from Portugal, Spain, Germany and Algeria, our data suggest that the sediment
supply to the Ediacaran–Early Palaeozoic siliciclastic sequences preserved in all these peri-
Gondwanan regions was similar. The lack of Grenvillian-aged (c. 1.1–0.9 Ga) zircon in the
Ossa–Morena and Saxo-Thuringia Ediacaran sediments suggests that the sediment in these
peri-Gondwanan basins was derived from the West African craton
Tracing the Cambro-Ordovician ferrosilicic to calc-alkaline magmatic
U–Pb geochronological study of zircons from nodular granites and Qtz-diorites comprising part of Variscan high-
grade metamorphic complexes in Gredos massif (Spanish Central System batholith) points out the significant
presence of Cambro-Ordovician protoliths among the Variscan migmatitic rocks that host the Late Carboniferous
intrusive granitoids. Indeed, the studied zone was affected by two contrasted tectono-magmatic episodes, Car-
boniferous (Variscan) and Cambro-Ordovician. Three main characteristics denote a close relation between the
Cambro-Ordovician protholiths of the Prado de las Pozas high-grade metamorphic complex, strongly reworked
during the Variscan Orogeny, and other Cambro-Ordovician igneous domains in the Central Iberian Zone of the
Iberian Massif: (1) geochemical features show the ferrosilicic signature of nodular granites. They plot very
close to the average analysis of themetavolcanic rocks of the Ollo de Sapo formation (Iberia). Qtz-diorites present
typical calc-alkaline signatures and are geochemically similar to intermediate cordilleran granitoids. (2) Both
Qtz-diorite and nodular granite samples yield a significant population of Cambro-Ordovician ages, ranging
between 483 and 473 Ma and between 487 and 457 Ma, respectively. Besides, (3) the abundance of zircon inher-
itance observed on nodular granites matches the significant component of inheritance reported on Cambro-
Ordovician metagranites and metavolcanic rocks of central and NW Iberia.
The spatial and temporal coincidence of both peraluminous and intermediate granitoids, and specifically in
nodular granites and Qtz-diorite enclaves of the Prado de las Pozas high-grade complex, is conducive to a
common petrogenetic context for the formation of both magmatic types.
Tectonic and geochemical characteristics describe the activity of a Cambro-Ordovician arc-back-arc tectonic set-
ting associated with the subduction of the Iapetus–Tornquist Ocean and the birth of the Rheic Ocean. The exten-
sional setting is favorable for the generation, emplacement, and fast rise of subduction-related cold diapirs,
supported by the presence of typical calc-alkaline cordilleran granitoids contemporary with ferrosilicic
volcanism
Inherited arc signature in Ediacaran and Early Cambrian basins of
Geochemical data from clastic rocks of the Ossa-Morena Zone (Iberian Massif) show that the main source for the Ediacaran
and the Early Cambrian sediments was a recycled Cadomian magmatic arc along the northern Gondwana margin. The geodynamic
scenario for this segment of the Avalonian-Cadomian active margin is considered in terms of three main stages: (1) The 570–540 Ma
evolution of an active continental margin evolving oblique collision with accretion of oceanic crust, a continental magmatic arc
and the development of related marginal basins; (2) the Ediacaran–Early Cambrian transition (540–520 Ma) coeval with important
orogenic magmatism and the formation of transtensional basins with detritus derived from remnants of the magmatic arc; and (3)
Gondwana fragmentation with the formation of Early Cambrian (520–510 Ma) shallow-water platforms in transtensional grabens
accompanied by rift-related magmatism. These processes are comparable to similar Cadomian successions in other regions of
Gondwanan Europe and Northwest Africa. Ediacaran and Early Cambrian basins preserved in the Ossa-Morena Zone (Portugal
and Spain), the North Armorican Cadomian Belt (France), the Saxo-Thuringian Zone (Germany), the Western Meseta and the
Western High-Atlas (Morocco) share a similar geotectonic evolution, probably situated in the same paleogeographic West African
peri-Gondwanan region of the Avalonian-Cadomian active margin
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